1. Field of the Invention
This invention pertains generally to HDTV and DTV transmitters, receivers and signal processing and decoding systems, and more particularly to mobile decoding of HDTV and an apparatus and method for processing a combined A/53 and A/153 standard broadcast signal with a single chip or device.
2. Description of Related Art
The fundamental problem to be overcome in wireless communications systems is to accurately receive and reproduce data transmitted through noisy channels. In order to achieve the ultimate goal of exactly reproducing the information sent through a memoryless noisy medium, various transmission and reception schemes have been developed. Some channel coding and de-coding systems try to protect transmissions from errors or other disturbances using redundancies and error correction.
Digital high definition television transmissions over terrestrial, cable, and satellite networks, for example, have been standardized. The Advanced Television Systems Committee, Inc. (ATSC), is an international, non-profit organization that has developed a set of voluntary standards for digital television transmissions among different communications media including digital broadcast television, interactive systems, and broadband multimedia communications.
Currently there are two standards, the A/53 HDTV standard and the A/153 Mobile DTV standard, which apply separately to different receivers. The receivers are designed to be separate; e.g., the public either has a mobile DTV receiver or a fixed HDTV receiver, but not a combined receiver. While A/153 operation fits into A/53 to concurrently supply mobile DTV data and HDTV data to the public from one transmitter source, the A/53 performance is not very good for high-dynamic channels.
The ATSC A/53 standard transmitter is shown in the functional block diagram of FIG. 1. It can be seen that the incoming data is randomized and then processed for forward error correction (FEC) in the form of Reed-Solomon (RS) coding, where 20 RS parity bytes are added to each MPEG-2 packet, one-sixth data field interleaving and two-thirds rate trellis coding.
By design, the A/53 Digital Television Standard uses the 6 MHz bandwidth that has been allocated to analog television channels. Depending on the method of transmission, the transport stream can be modulated in various ways once the digital video and audio signals have been compressed and multiplexed by the transmitter.
An ATSC A/53 standard receiver is shown in the functional block diagram of FIG. 2. The ATSC/8VSB A/53 receiver, receives, demodulates, decodes and analyzes 8VSB (eight-level vestigial sideband) signals. The MPEG 2 transport stream is demultiplexed, decompressed and AV synchronized and formatted for the specific television of the user.
The ATSC M/H (mobile/handheld) standard (A/153) allows delivery of multimedia to mobile DTV-equipped cellphones, tablets, laptops, netbooks, in-car navigation systems and other mobile devices. Like the A/53 system, the ATSC Mobile DTV (A/153) scheme is based on vestigial sideband (VSB) modulation, along with some additional error correction mechanisms, and shares the same RF channel as A/53 by using a portion of the total available 19.4 Mb/s bandwidth.
The functional diagrams of FIG. 3A and FIG. 3B, show an A/153 standard transmitter and FIG. 4 illustrates a corresponding A/153 receiver. Generally, the ATSC-M/H (A/153) standard defines a virtual frame structure that is called an M/H Frame that has a fixed duration of 968 ms. The M/H frame consists of 5 M/H subframes and each M/H subframe has 16 M/H numbered slots called M/H-groups. One virtual M/H frame is based on 20 VSB frames (12,480 transport stream packets) and has an offset of 37 transport stream packets to the VSB frame structure.
Although the A/53 HDTV and the A/153 Mobile DTV transmissions can be made from a single source, the corresponding receivers are separate. Accordingly, there is a need for an apparatus and system that can receive and perform both the A/53 standard and A/153 standard transmissions across many different platforms. The present invention satisfies this need, as well as others, and is generally an improvement in the art.